Due to rapid improvements in the efficiency of solar cells using organolead perovskites (APbX3), organolead perovskites have been the focus of much attention and many diverse production methods have been reported. Among these, Non-patent Document 1 describes that an organolead perovskite was produced by heater-heated codeposition, and that a high solar cell efficiency was obtained by the resulting organolead perovskite. Additionally, Patent Document 1 and Non-patent Document 2 describe that an organic-inorganic composite perovskite containing an organolead perovskite was formed by codeposition.
In order to form organolead perovskite by codeposition, an organic material (AX) and a lead halide (PbX2) must be simultaneously or alternately evaporated.
However, many of the organic materials (AX) that are used in such codeposition are materials having high vapor pressures, so there are problems in that the organic materials can vaporize in the vacuum chamber and greatly degrade the vacuum level, the vaporized material may spread and contaminate the other raw materials that are to be deposited and the like, and the film deposition rate may run out of control. These problems have a significant impact, not only on the film formation process, but also on the film quality of the formed thin-film.
For this reason, the precedent literature, such as Non-patent Document 1, describes that the film formation of an organolead perovskite having a certain level of film quality was possible, but it can be assumed that there were considerable difficulties in finding stable codeposition conditions and that long-term stable codeposition was mostly impossible, and it can also be assumed that there is much room for improvement in the film quality of the formed thin films.